Kepler spots two super Earths, one squarely in the habitable zone

Planets are about 1.5 times Earth's radius—and the right distance from a host star.

Liquid water is one of the essential ingredients of life on Earth and it has properties conducive to life in general, so researchers have defined the concept of a habitable zone with water as its focus. For astronomers, the habitable zone is the area far enough from a host star that a planet would be cool enough to support liquid water, but not so far that the water would be frozen. Although there are many caveats to this definition—everything from the presence of greenhouse gasses to clouds will shift a planet's average surface temperature—the concept helps drive the search for a planet capable of supporting life.

The caveats, however, have led to a number of arguments over whether a given exoplanet is likely able to host liquid water, with some candidates shifting in and out of the habitable zone more than once. Still, it's pretty clear that given the largenumber of reportedcandidateexoplanets, the odds suggest we've already spotted one. Today, scientists are announcing an exosolar system that has two planets that are both likely to be within the habitable zone, along with three others that are closer to the host star.

The findings come from the Kepler mission, which is dealing with a backlog of roughly 2,000 planet candidates to sort through and confirm. Normally, confirmation requires observing changes in the light emitted by the host star, which gets dragged closer to and further from the Earth as the planets circle it. However, this method requires that the planets either be large or orbiting close to the star so that their gravitational influence is big enough to shift it.

The new exosolar system, Kepler-62, couldn't be confirmed that way, in part because the planets orbiting it are simply too small. Measured in terms of the Earth, the five planets are 1.31, 0.54, 1.95, 1.61, and 1.41 Earth radii, in order of their distance from the host star. These measurements make the second planet, Kepler-62c, one of the smallest exoplanets yet spotted. The researchers refer to it as a "hot Mars," due to its proximity to the host star.

To confirm that the changes in the star's light were likely caused by planets passing in front of it, the authors calculated the odds of the changes resulting from a variety of alternatives. These include things like a complex system of stars orbiting each other or a chance confluence of stars at different distances from Earth. In every case, a system of planets ended up being thousands of times more likely to be the cause of the light changes from Kepler-62.

So what can we tell about the nature of these planets? Normally, the same method to directly confirm that they were planets would have told us something about their masses, which would allow us to calculate their density and infer their composition. In the absence of that data, all the authors have to go on is a statistical inference: in the systems where we do have a measure of the planet's composition, bodies this size tend to be rocky, so the planets of the Kepler-62 system are most likely rocky as well. The star is old enough, at about 7 billion years, that any heat from formation has long since dissipated, which means the bodies would be solid rather than molten.

The three inner planets are clearly close enough to the star that they would be far too hot to support liquid water—their orbital periods are 5.7, 12.4, and 18.2 days. But from there out, the spacing gets much broader, at 122.4 and 267.3 days. Given the luminosity of their host star, the spacing means that the outer two get somewhat closer to Earth-like amounts of light: 1.2 and 0.41 times the solar flux that the Earth receives. This revelation raises the prospect that they might be able to support liquid water.

Assuming a cloud-free atmosphere of carbon dioxide, nitrogen, and water vapor, this amount of light would place Kepler-62e (the fourth planet) just inside of the habitable zone. It's worth noting, however, that Earth sits right on the inner edge of this boundary, and it supports lots of liquid water (so this is likely just a rough guideline). Based on the brightness of the star, the authors place Kepler-62e well inside what they call the "empirical habitable zone," meaning it should be cooler than Venus. Kepler-62f, however, is squarely within both the calculated and empirical habitable zones.

The authors caution that "We do not know if Kepler-62e and -62f have a rocky composition, an atmosphere, or water." Given its distance from the Sun, we're not going to know any of those things about these planets any time soon. If we find enough systems that look like Kepler-62, the odds will be raised that we'll be able to find something simliar that's within the range of telescopes we can put into orbit.

In all seriousness, the atmosphere is the big question here, correct? These bodies could be dead planetoids like the moon with no atmosphere to sustain life, regardless of their place in the hospitable zone. We can't really tell if that's the case yet, as the article states.

So, if/when we get around to colonizing places like this in the semi-distant future, seeing as all infrastructure would be from scratch, what are the odds the colonists lose most or all of the tech within a few generations?

This article seems to be missing a lot of valuable information... that or I'm just really oblivious right now.

After reading the article, I don't know:

- How far away this star is in lightyears.- Who these scientists are, other than being associated with the Kepler mission in some way.- How statistical inference can be nearly good enough.- - We can't even confirm the planets' existence using normal methods, from what I gathered in the article, they have to be inferred from the lack of other effects... yet somehow we're determining the number of planets, their individual radii, their orbital radii, and more.

So, if/when we get around to colonizing places like this in the semi-distant future, seeing as all infrastructure would be from scratch, what are the odds the colonists lose most or all of the tech within a few generations?

That's okay. They then become space cowboys. They have their ship to bring them work, and a gun to help them keep it.

So, if/when we get around to colonizing places like this in the semi-distant future, seeing as all infrastructure would be from scratch, what are the odds the colonists lose most or all of the tech within a few generations?

Depends, I would guess it's fairly unlikely. The reasons it could happen (imo) would be if we were to establish a colony either without ftl travel or simply to far away for trade to be viable. That in combination with the population being low enough for that to happen (< 10000).

Add then that it's likely a decent ammount of resources will have to be spent terraforming before the fact. I'd think the most likely cause for such a colony would be religious fundamentalists wanting to get away from terra.

It's interesting to note, Ars Technica, that I went to downvote a spam post and I got a popup saying "parse error". Of course, when I refreshed the page, the post was gone. Not sure if you want me seeing "parse error" in those instances. Perhaps something like "We deleted spam comment." I'm sure my request to downvote includes some kind of ID, and you could store the IDs of the delete spam items in a table and do a check against that table if the ID I send isn't found or is marked "deleted". Blah blah.

I'm not going to do the math just now, but gravity on the surface of a planet is inversely related to the distance squared to the core.

In other words, while the gravitational strength of the planet grows exponentially to its radius, what you feel decreases by the same rate relative to the radius. I believe you could have a planet with twice the radius and yet have Earth-like surface gravity, as long as the density is similar.

It's interesting to note, Ars Technica, that I went to downvote a spam post and I got a popup saying "parse error". Of course, when I refreshed the page, the post was gone. Not sure if you want me seeing "parse error" in those instances. Perhaps something like "We deleted spam comment." I'm sure my request to downvote includes some kind of ID, and you could store the IDs of the delete spam items in a table and do a check against that table if the ID I send isn't found or is marked "deleted". Blah blah.

The best thing to do with spam posts is to report them (by clicking on the yellow triangle icon) instead of downvoting. To your point, I did try reporting that spam post and got a moonshark.

Very back of envelope: assume density=earthvolume = 4/3 pi (1.61)^3 so mass is 17.4 earth.

9.8 x 17.4 x (1/1.61)^2

6.62 times gravity. I could easily have borked it up.

Wouldn't it have 4.17 times the earth's mass? Which would get me 1.61 times the gravity...

Original poster forgot to take into account 4pi/3 for earth. And as you said, since mass is proportionate to r^3, and gravity is inversely proportionate to R^2 (R being object's distance from the center of mass), at the planet's surface gravity would be 1.61gs.

edit: first part of my post was chopped, and then I realized that much of my post was redundant..

It's worth noting, however, that Earth sits right on the inner edge of this boundary

If I interpret this statement correctly, we are "on the warm side" of habitable?

i seem to recall reading somewhere long ago (so long ago, that pluto was still considered a planet) that VENUS was on the inner edge of the habitable zone, but because of its excessive volcanism and greenhouse gasses, it is way too hot for life as we know it. and on the same vein, mars is also considered to be on the outer fringe of the habitable zone, and it's too cold because it doesn't have enough atmosphere to hold heat.

of course that was practically last century that i remember that from, so things could have been redefined (witness pluto) or i could simply be remembering incorrectly - so please feel free to /trout me if i'm wrong.

It would be quite amazing if both of those planets in the habitable zone had liquid water and life. Can you imagine if Mars was that easily colonized? Our definition of life is so narrow. Being able to study life from another planet -- even within our own solar system -- would provide incredible insight. Being able to study life from 2 planets within another solar system would be even more incredible.

It's worth noting, however, that Earth sits right on the inner edge of this boundary

If I interpret this statement correctly, we are "on the warm side" of habitable?

Seems like a stretch considering how much time the globe spends in ice ages. I would not want us to be much farther from the sun.

i seem to recall reading somewhere long ago (so long ago, that pluto was still considered a planet) that VENUS was on the inner edge of the habitable zone, but because of its excessive volcanism and greenhouse gasses, it is way too hot for life as we know it. and on the same vein, mars is also considered to be on the outer fringe of the habitable zone, and it's too cold because it doesn't have enough atmosphere to hold heat.

of course that was practically last century that i remember that from, so things could have been redefined (witness pluto) or i could simply be remembering incorrectly - so please feel free to /trout me if i'm wrong.

New nights and weekends project: find a way to switch Mars and Venus' orbits, that way we got 3 viable planets.

It would be quite amazing if both of those planets in the habitable zone had liquid water and life. Can you imagine if Mars was that easily colonized? Our definition of life is so narrow. Being able to study life from another planet -- even within our own solar system -- would provide incredible insight. Being able to study life from 2 planets within another solar system would be even more incredible.

If Mars had life it would probably almost impossible to colonize because of potential biohazards. Didn't you read War of the Worlds...Gosh!

It would be quite amazing if both of those planets in the habitable zone had liquid water and life. Can you imagine if Mars was that easily colonized? Our definition of life is so narrow. Being able to study life from another planet -- even within our own solar system -- would provide incredible insight. Being able to study life from 2 planets within another solar system would be even more incredible.

If Mars had life it would probably almost impossible to colonize because of potential biohazards. Didn't you read War of the Worlds...Gosh!

That, and if you've watched the historical documentaries (read Star Trek... ), you would know that solar systems which have life on two or more planets are usually at war with each other.

If I interpret this statement correctly, we are "on the warm side" of habitable?

Seems like a stretch considering how much time the globe spends in ice ages. I would not want us to be much farther from the sun.

Just at the warm edge, in fact. I don't know the details of their modeling, but I can think of some possible explanations.

Note that while we've had ice ages, we don't appear to have actually had a global freeze, and it looks like CO2 buildup can do a lot to prevent such an event. And we have had periods without icecaps, at which times the planet had relatively little margin for tolerating further heating before the planet would turn into a steambath with runaway greenhouse effect due to water vapor.

Also recall that the planet had to stay cool enough for life to form and thrive even before it had its current oxy-nitrogen atmosphere. The inner edge may be the distance a young planet with a dense atmosphere rich in greenhouse gases requires in order to keep liquid water.

Did anyone read the linked article? they're saying they think both of these planets are completely covered with water, with no visble land at all - waterworlds - and maybe not even much of an atmosphere. seems to be an awful lot of conjecture just based on a few transits...

It's worth noting, however, that Earth sits right on the inner edge of this boundary

If I interpret this statement correctly, we are "on the warm side" of habitable?

Seems like a stretch considering how much time the globe spends in ice ages. I would not want us to be much farther from the sun.

i seem to recall reading somewhere long ago (so long ago, that pluto was still considered a planet) that VENUS was on the inner edge of the habitable zone, but because of its excessive volcanism and greenhouse gasses, it is way too hot for life as we know it. and on the same vein, mars is also considered to be on the outer fringe of the habitable zone, and it's too cold because it doesn't have enough atmosphere to hold heat.

of course that was practically last century that i remember that from, so things could have been redefined (witness pluto) or i could simply be remembering incorrectly - so please feel free to /trout me if i'm wrong.

New nights and weekends project: find a way to switch Mars and Venus' orbits, that way we got 3 viable planets.

Not sure about Venus, but a lack of magnetic field on mars is probably a bigger problem than it's temperature.

Not sure about Venus, but a lack of magnetic field on mars is probably a bigger problem than it's temperature.

Not a significant problem. Mars is further away from the Sun; surface radiation would be about the same as astronauts in orbit (i.e. manageable at early colony stages, and easily manageable when permanent underground settlements are built).

Don't say that. Someone might buy a piece of land in some very remote place and build a rocket connected to a big solar farm that collects solar energy during the day and then uses the stored energy to fire the rocket straight up into the sky all night long.